I would give it to the A's, with Loiza playing great, Loaiza was 4-0 with a 1.48 ERA the past month, and even Saarloss is playing great, Saarloos was 4-0 with a 2.01 ERA, but I dont expect him to continue pitching like that, but adds great depth in the bullpen knowing he can go 5+ innings pitching great.
In the last 30 games Oakland starters are 19-7 with a 3.97 ERA. In August, Esteban Loaiza, Barry Zito, Dan Haren, Joe Blanton and Kirk Saarloos went 19-4 with a 2.82 ERA.

When Harden comes back healthy, the A's would be a tough team to beat in the playoffs.
The offense is also coming around, Ellis is being picked up in deeper leagues, Thomas is continueing playing great, Jason Kendall's bat has stopped shrinking, and swiping bags. Swisher isn't looking like the swisher of last month.
The team who had the best rotation and bullpen in the AL west used to be the Angels

Oakland hands down, to have zito, haren(last three starts have been shaky), Loiza, Blanton, Saarloss going into either a best of 5 or 7 is a good bet Oakland won't choke. If Harden does come back, the a's need to ease him in the games by the bullpen.